[PATCH RFC v1 1/2] documentation/iommu: Add description of Hisilicon System MMU binding

leizhen
2014-06-17T07:57:28Z

On 2014/6/17 0:42, Arnd Bergmann wrote:
> On Monday 16 June 2014 17:26:53 Will Deacon wrote:
>> On Fri, Jun 06, 2014 at 12:07:11PM +0100, Dave Martin wrote:
>>> On Fri, Jun 06, 2014 at 08:48:26AM +0200, Arnd Bergmann wrote:
>>>> On Thursday 05 June 2014 21:37:09 Zhen Lei wrote:
>>>>
>>>>> +- smmu-masters : A list of phandles to device nodes representing bus
>>>>> + masters for which the SMMU can provide a translation
>>>>> + and their corresponding StreamIDs (see example below).
>>>>>
>>>>
>>>> We're currently in the process of defining a generic binding for IOMMUs.
>>>>
>>>> While the smmu-masters property was copied from an existing binding,
>>>> I think we will end up migrating away from that towards a common way
>>>> to express those things, and we shouldn't add another one doing this
>>>> in a nonstandard way. Please have a look at the latest discussion
>>>> about the iommu binding using #iommu-cells and a reference from the
>>>> master to the iommu and see if you can migrate your code to use that.
>>>
>>> Thanks for making this point -- I was going to do so yesterday but then
>>> hesitated due to uncertainty about whether this should really be a new
>>> driver.
>>>
>>> Either way, it would be very valuable at least to attempt to describe
>>> the Hisilicon SMMU implemenation using the new proposals, since that is
>>> a good test of how reusable the proposed generic binding actually is.
>>
>> If this ends up being an addition to the existing ARM SMMU driver, I'm
>> really not keen on using the new DT bindings. We're already stuck with
>> the old bindings for that driver -- supporting both old and new in the
>> same code only buys us maintenance headaches and pointless divergence
>> within the driver.
>
> We have to migrate the driver to the new binding anyway, it may be
> a bit painful, but there are not really any users yet so there
> is a chance we can remove the nonstandard code at some point,
> perhaps in a few years.
>
> Arnd
>
> .
>
My driver will base on arm-smmu, and I saw Will Deacon had agreed to you.
So me too.